Add some docs for mipmap level access.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@3272 dfc29bdd-3216-0410-991c-e03cc46cb475

include/ITexture.h

@@ -94,7 +94,11 @@ public:
 	pixels. After lock() has been called and all operations on the pixels
 	are done, you must call unlock().
 	Locks are not accumulating, hence one unlock will do for an arbitrary
-	number of previous locks.
+	number of previous locks. You should avoid locking different levels without
+	unlocking inbetween, though, because only the last level locked will be
+	unlocked.
+	The size of the i-th mipmap level is defined as max(getSize().Width>>i,1)
+	and max(getSize().Height>>i,1)
 	\param readOnly Specifies that no changes to the locked texture are
 	made. Unspecified behavior will arise if still write access happens.
 	\param mipmapLevel Number of the mipmapLevel to lock. 0 is main texture.
@@ -105,7 +109,8 @@ public:
 	virtual void* lock(bool readOnly = false, u32 mipmapLevel=0) = 0;
 
 	//! Unlock function. Must be called after a lock() to the texture.
-	/** One should avoid to call unlock more than once before another lock. */
+	/** One should avoid to call unlock more than once before another lock.
+	The last locked mip level will be unlocked. */
 	virtual void unlock() = 0;
 
 	//! Get original size of the texture.
@@ -133,7 +138,7 @@ public:
 	/** \return The color format of texture. */
 	virtual ECOLOR_FORMAT getColorFormat() const = 0;
 
-	//! Get pitch of texture (in bytes).
+	//! Get pitch of the main texture (in bytes).
 	/** The pitch is the amount of bytes used for a row of pixels in a
 	texture.
 	\return Pitch of texture in bytes. */
@@ -149,11 +154,19 @@ public:
 	}
 
 	//! Regenerates the mip map levels of the texture.
-	/** Required after modifying the texture, usually after calling unlock(). */
+	/** Required after modifying the texture, usually after calling unlock().
+	\param mipmapData Optional parameter to pass in image data which will be
+	used instead of the previously stored or automatically generated mipmap
+	data. The data has to be a continuous pixel data for all mipmaps until
+	1x1 pixel. Each mipmap has to be half the width and height of the previous
+	level. At least one pixel will be always kept.*/
 	virtual void regenerateMipMapLevels(void* mipmapData=0) = 0;
 
 	//! Check whether the texture is a render target
-	/** \return True if this is a render target, otherwise false. */
+	/** Render targets can be set as such in the video driver, in order to
+	render a scene into the texture. Once unbound as render target, they can
+	be used just as usual textures again.
+	\return True if this is a render target, otherwise false. */
 	virtual bool isRenderTarget() const { return false; }
 
 	//! Get name of texture (in most cases this is the filename)